JP2002243787A - Insulation monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation monitoring device capable of adequately taking measures for insulation such as rechecking, repairing, replacing components and the like, and also capable of preventing an accident caused by an insulation failure. SOLUTION: The feature of this invention is that plural current transformers 12 to detect a leakage current generated when insulation deterioration is caused in a part of a low voltage distribution lines 8, 9 and loads 10, 11, a relay unit 13 to take in the detected values of these current transformers 12 one by one, and an insulation monitoring device 15 having a function capable of either displaying a picture, copying, printing or giving a warning, by processing a signal based on the detected value of the current transformer are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention monitors the deterioration state of the insulation resistance of a load system such as electric equipment and cables installed in a building or the like, and alerts the user when the insulation resistance falls below a predetermined insulation resistance. The present invention relates to an insulation monitoring device for enabling a load system to be appropriately repaired and cut off.

[0002]

2. Description of the Related Art Various types of electrical equipment installed in buildings and factories are deteriorated in insulation resistance and dielectric breakdown voltage due to long-term use. The degree of insulation resistance deterioration of electrical equipment varies depending on the installation environment, particularly dust, temperature, humidity and the like. Due to this deterioration, malfunction of equipment and fire may occur.To prevent this, periodic inspections of important equipment are conducted by service personnel of our company and maintenance company, and insulation resistance deteriorates below the specified value. If so, repair and replacement of the target electrical equipment and parts are performed.

[0003] In some equipment, even if the insulation deterioration is less than the specified value, the interruption is not permitted at that time, and it is not possible to detect the abnormality and operate the circuit breaker.
Therefore, periodic inspection is very important. If it is known beforehand that the time of use becomes unusable with respect to the allowable limit of insulation deterioration, equipment, repair parts and the like can be prepared, and a normal state can be restored while operating in parallel at a predetermined time.

[0004] In order to monitor the deterioration of the insulation resistance of the electric equipment, the method of detecting the leakage current of the power distribution line is described in, for example, JP-A-9-218237.

[0005]

However, periodic inspections are performed approximately once a year. If the insulation of equipment and equipment rapidly deteriorates for some reason and exceeds the specified value by the next inspection, Had a problem that it was not possible to respond adequately.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks. It is an object of the present invention to provide an insulation monitoring device capable of always monitoring insulation deterioration and preventing an insulation failure accident of electrical equipment and cables. Is to do.

[0007]

A feature of the present invention is that a leakage current of a distribution line feeding a load is detected, a trend thereof is displayed, and a deterioration state of the insulation resistance is determined. is there.

[0008]

FIG. 1 is a block diagram showing an insulation monitoring device according to the present invention. In addition, the target electrical equipment etc. are installed in the part G separated by the dotted line on the left side of FIG.

In FIG. 1, 1 is a high voltage line of a distribution line,
For example, three-phase, 3.3 kV, high-voltage lines 4 and 5 are formed via circuit breakers 2 and 3, and converted into low-voltage lines 8 and 9 by transformers 6 and 7, respectively. Low pressure line 8 is three phase, 220
V, low voltage line 9 is single phase, 110V. A load group 10 is connected to each of the three-phase low-voltage lines 8, and a load group 11 is connected to each of the single-phase low-voltage lines 9. Reference numeral 12 denotes a current transformer such as a zero-phase current transformer, which detects a leakage current generated when insulation of each load system is deteriorated, and a plurality of current transformers are provided for a predetermined load. When the insulation state of these load groups 10 and 11 is sound, the detection current of the current transformer 12 is zero because no leakage current occurs.

[0013] Reference numeral 13 denotes a relay unit to which the detected currents of the plurality of current transformers 12 are input and sequentially sent to the control device 14. Reference numeral 15 denotes an insulation monitoring device, which is installed in the monitoring room R on the left side of the dotted line, and controls each load group
The insulation status of 0 and 11 is monitored.

FIG. 2 is a diagram showing a principle of detecting a leakage current by the current transformer 12.

The current transformer 12 is installed in a loop so as to surround the distribution line 16 to the load groups 10 and 11, and the power supply system of the load groups 10 and 11 has no insulation failure (A in FIG. 2). In the normal state shown in ()), the leakage current does not occur, and the detection value of the current transformer 12 is zero.

When insulation deterioration occurs in a part of the load groups 10 and 11, a leakage current Δi flows to the ground as shown in FIG. Due to this leakage, the above-mentioned state collapses and becomes unbalanced, and a current corresponding to this is detected in the current transformer 12. Similar current detection is performed even if insulation failure occurs in the cables constituting these power supply systems in addition to the load groups 10 and 11.

When the power supply has three phases, the three lines are balanced by the load current when there is no insulation deterioration.
No so-called zero-phase current flows. If insulation is deteriorated and this balance is lost, a detection current flows through the current transformer 12 as described above.

The detected current is sent to the control device 14 via the relay unit 13, and a predetermined signal processing is performed. The processed signal indicates the insulation deterioration state by the insulation monitoring device 15.
To enable screen display, printing, printing, alarm generation, and the like.

For the insulation monitoring device 15, it is convenient to use, for example, a personal computer (personal computer) so that the screen display of data based on the processing signal, the graph display processed by the data, and the driving of a printing machine installed outside can be easily performed. is there.

FIG. 3 is an example of a screen display, and is a history graph in which the insulation resistance at the date and time on the horizontal axis is converted into the detected current value and is expressed on the vertical axis. FIG. 4 shows the numerical value history data.

The change state of the insulation resistance of a certain load system is
This is an example of measurement at a frequency of every minute, and FIG. 3 is a graph in which measurement points are plotted and displayed. FIG. 4 shows the numerical data, and the current setting levels 1 and 2 are indicated by white circles when the detected current value is equal to or lower than those levels, and are indicated by black circles when the detected current value is higher than these levels.

For example, for electrical equipment or its system,
Assuming that the allowable deterioration limit of the insulation resistance that requires repair is 500 mA in terms of the detected current value, set the levels 1 and 2 at 20% and 40% of that value, and inform them that they are approaching the allowable deterioration limit. Arousing and predicting the future. So-called trend management becomes possible, so that the part can be rechecked, repaired or replaced parts can be prepared before it becomes important.

In addition, in the case of electrical equipment in which it is inconvenient to shut off the power supply during use, for example, an elevator, even if the insulation deterioration has progressed to some extent, it cannot be shut off at that time for safety. Therefore, in this case, inspection and repair will be performed during the downtime of the elevator. Others
In equipment at a steel mill, replacement equipment is prepared before the deterioration state reaches an allowable limit, and the state can be switched to a healthy state while operating in parallel.

The measurement frequency is set to an arbitrary value such as several minutes to several tens of minutes depending on the electric equipment. If the frequency is set to be the same, the relay unit 13, the control device 14, and the monitoring device 15
Therefore, it is advisable to set the frequency to an appropriate frequency according to the importance of the electrical equipment and the degree of progress of the insulation resistance deterioration that is empirically known.

[0022]

According to the present invention, insulation deterioration is always monitored, and reinspections, repairs, parts replacement, etc. concerning insulation of electrical equipment and power cables can be appropriately performed, and insulation failure accidents can be prevented beforehand. To play.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an insulation monitoring device according to the present invention.

FIG. 2 is a diagram showing a principle of detecting a leakage current by a current transformer.

FIG. 3 is an example of a screen display according to the present invention.

FIG. 4 is numerical history data of FIG.

[Explanation of symbols]

 1, 4, 5 ... high voltage line, 6 ... 3 phase-3 phase transformer, 7 ... 3 phase-single phase transformer, 8 ... 3 phase low voltage line 9 ... single phase low voltage line, 10 ... 3 phase load group 11 ... Single-phase load group, 12: Current transformer, 13: Relay unit 14: Control device, 15: Insulation monitoring device, 16: Distribution line, 17: Distribution line

Claims (2)

[Claims] 1. A current transformer for detecting a leakage current of a distribution line for feeding a load, and an insulation for inputting a detection value of the current transformer and displaying a trend thereof to judge a deterioration state of an insulation resistance. An insulation monitoring device, comprising: monitoring means. 2. A plurality of current transformers for respectively detecting zero-sequence currents of a plurality of distribution lines supplying power to a load, a relay unit for sequentially taking in the detected values of these current transformers, and a relay unit. A personal computer for inputting a detected value of the current transformer, displaying a trend thereof, and judging a deterioration state of the insulation resistance.